The invention relates to a controller for a motor, and particularly, a controller for a motor operating a pump.
Occasionally on a swimming pool, spa, or similar jetted-fluid application, the main drain can become obstructed with an object, such as a towel or pool toy. When this happens, the suction force of the pump is applied to the obstruction and the object sticks to the drain. This is called suction entrapment. If the object substantially covers the drain (such as a towel covering the drain), water is pumped out of the drain side of the pump. Eventually the pump runs dry, the seals burn out, and the pump can be damaged. Alternatively, the object itself can become damaged when stuck to the drain.
Another type of entrapment is referred to as mechanical entrapment. Mechanical entrapment occurs when an object, such as a towel or pool toy, gets tangled in the drain cover. Mechanical entrapment may also effect the operation of the pump.
Several solutions have been proposed for suction and mechanical entrapment. For example, new pool construction is required to have two drains, so that if one drain becomes plugged, the other can still flow freely and no vacuum entrapment can take place. This does not help existing pools, however, as adding a second drain to an in-ground, one-drain pool is very difficult and expensive. Modern pool drain covers are also designed such that items cannot become entwined with the cover.
As another example, several manufacturers offer systems known as Safety Vacuum Release Systems (SVRS). SVRS often contain several layers of protection to help prevent both mechanical and suction entrapment. Most SVRS use hydraulic release valves that are plumbed into the suction side of the pump. The valve is designed to release (open to the atmosphere) if the vacuum (or pressure) inside the drain pipe exceeds a set threshold, thus releasing the obstruction. These valves can be very effective at releasing the suction developed under these circumstances. Unfortunately, they have several technical problems that have limited their use.